Cellular phones or other electronic devices are the devices people use on a daily basis, which utilize processors to handle lots of signal manipulation calculations, deal with commands and control signaling, and coordinate other operations of other internal circuits of the cellular phones or the electronic devices.
Generally, a processor or other internal circuits of the cellular phone or the electronic device requires two external crystal oscillators. Please refer to FIG. 1, which schematically illustrates clock generation architecture of a conventional electronic device 10. A first crystal oscillator 110 provides a low frequency clock signal to internal circuits 130 for mobile communications in a standby state mode, such as a sleep/wake-up clock and real-time clock (RTC), while a second crystal oscillator 120 provides a high frequency clock signal to internal circuits 130 for high frequency applications.
Although the crystal oscillator has good characteristics, such as low temperature coefficient and moderate power consumption, and it is also able to provide an accurate and precise clock signal, the hardware cost of the crystal oscillator is still considerable.